Re: [Qemu-devel] [PATCH v7 00/10] Drop in_use from BlockDriverState and enable point-in-time snapshot exporting over NBD

[Fam Zheng <famz@redhat.com>]

On 2013年12月13日 10:40, Ian Main wrote:
> On Thu, Dec 12, 2013 at 04:23:36PM +0800, Fam Zheng wrote:
>> This series adds for point-in-time snapshot NBD exporting based on
>> blockdev-backup (variant of drive-backup with existing device as target).
>>
>> We get a thin point-in-time snapshot by COW mechanism of drive-backup, and
>> export it through built in NBD server. The steps are as below:
>>
>>   1. (SHELL) qemu-img create -f qcow2 BACKUP.qcow2 <source size here>
>>
>>      (Alternatively we can use -o backing_file=RUNNING-VM.img to omit explicitly
>>      providing the size by ourselves, but it's risky because RUNNING-VM.qcow2 is
>>      used r/w by guest. Whether or not setting backing file in the image file
>>      doesn't matter, as we are going to override the backing hd in the next
>>      step)
>>
>>   2. (QMP) blockdev-add backing=source-drive file.driver=file file.filename=BACKUP.qcow2 id=target0 if=none driver=qcow2
>>
>>      (where source-drive is the running BlockDriverState name for
>>      RUNNING-VM.img. This patch implements "backing=" option to override
>>      backing_hd for added drive)
>>
>>   3. (QMP) blockdev-backup device=source-drive sync=none target=target0
>>
>>      (this is the QMP command introduced by this series, which use a named
>>      device as target of drive-backup)
>>
>>   4. (QMP) nbd-server-add device=target0
>>
>> When image fleecing done:
>>
>>   1. (QMP) block-job-complete device=source-drive
>
> If you do another revision, this should be block-job-cancel.
>

OK, thanks for reminding.

Fam